Answer: The system of equations that could be used to determine the number of small cups sold and the number of large cups sold is
6x + 18y = 780
y = 4x
Step-by-step explanation:
Let x represent the number of small cups that were sold.
Let y represent the number of large cups that were sold.
Each small cup holds 6 ounces of lemonade and each large cup hold 18 ounces of lemonade. Lincoln used 780 ounces. This is expressed as
6x + 18y = 780- - - - - - - - - - 1
Lincoln sold 4 times as many large cups as small cups. This is expressed as
y = 4x